1. Field of the Invention
The present invention relates to an apparatus for cutting a sheet-shaped material, which permits it to accurately and smoothly cut a sheet-shaped material formed of synthetic resin or the like.
2. Description of the Related Art
Various sheet-shaped materials such as Fresnel lens sheets, lenticular lens sheets or the like can be manufactured in accordance with a method as illustrated in FIGS. 7 and 8.
FIGS. 7 and 8 illustrate an example of a method for manufacturing a Fresnel lens sheet. First, a forming die 1 for the Fresnel lens is prepared and ultraviolet ray curing type resin 2 in the form of a liquid is dripped on a side of the forming die 1 (see FIG. 7(A)). Then, a substrate sheet 3 formed of a rigid synthetic resin is placed on the forming die 1. The substrate sheet 3 and the forming die 1 with the dripped resin are supplied into a space between a pair of nip rollers 4 (see FIG. 7(B)). A pressing operation, which is applied to the forming die 1 and the substrate sheet 3 by the nip rollers 4, causes the liquid ultraviolet ray curing type resin to flow and spread between the forming die 1 and the substrate 3. The ultraviolet ray curing type resin 2 is supplied in a relatively large amount so as to spread all over recess portions of the forming die 1. A superfluous amount of resin 2a flows out of the forming die 1 to reach the outside of the four peripheral sides thereof when carrying out a pressing operation by means of the nip rollers 4. A receiving member 1a for receiving the superfluous amount of resin 2a is provided on the four peripheral sides of the forming die 1 to project outside therefrom. The forming die 1, which has passed the nip rollers 4, is subjected to radiation of ultraviolet rays from above the substrate sheet 3 to cure the ultraviolet ray curing type resin 2. After curing is complete, the substrate, onto which the ultraviolet ray curing type resin 2 adheres, is removed from the forming die 1, thus preparing a sheet 5 of Fresnel lens as a semi-finished product (see FIGS. 7(C) and 8(A)).
The thus prepared sheet 5 of Fresnel lens as the semi-finished product has a larger size than the prescribed size of the Fresnel lens sheet to be used as the finished product and is provided with unwanted portions onto which the superfluous amount of resin 2a adheres. Accordingly, the sheet 5 is cut along the four cutting lines CL1, CL2, CL3 and CL4 as shown in FIG. 8(A). As a result, there is obtained a square or rectangular sheet 6 of Fresnel lens having the prescribed size as shown in FIG. 8(B).
It is necessary to cut the sheet 5 of Fresnel lens as the semi-finished product along the four cutting lines to remove the unwanted portions from the sheet 5 as described above. A conventional apparatus for cutting a sheet-shaped material, which is disclosed in Japanese Laid-Open Patent Application No. H11-300687, has been used to prevent cracks from occurring on the finished product side and burrs from occurring on the cutting surface when carrying out the above-mentioned cutting operation.
The conventional apparatus for cutting a sheet-shaped material is provided with a pair of blades, i.e., upper and lower blades, and holding members. The upper and lower blades face each other in the vertical direction so that the sheet-shaped material 5 of the semi-finished product is supplied horizontally and placed between the upper and lower blades. The holding members, which are made of material having a cushioning property, are disposed on the opposite sides of the lower blade. The holding members come into contact with the sheet-shaped material 5 when cutting it by means of the upper and lower blades. When the cutting operation starts to cut the sheet-shaped material 5, the upper blade comes into contact with the sheet-shaped material 5, prior to contact of the lower blade with the sheet-shaped material 5, so as to urge the sheet-shaped material on the holding members to be resiliently bent, and then, the lower blade comes into contact with the sheet-shaped material 5 thus bent.
However, in the conventional apparatus for cutting a sheet-shaped material, a superfluous amount of resin 2a, adhering on the sheet-shaped material as the semi-finished product, exerts an adverse influence during the cutting operation, causing the occurrence of cracks on the finished product side and burrs on the cutting surface, decreasing the cutting depth of the conventional apparatus tends to ease the occurrence of the above-mentioned cracks and burrs.
An object of the present invention is to provide an apparatus for cutting a sheet-shaped material, which makes it possible to accurately cut the sheet-shaped material without the occurrence of cracks on the finished product side and burrs on the cutting surface of the finished product.
In order to attain the aforementioned object, the apparatus of the first aspect of the present invention comprises: a first blade; a second blade disposed to face said first blade so that a sheet-shaped material to be cut is placed between said first blade and said second blade; first holding members disposed on opposite sides of said first blade, each of said first holding members being formed of self-deformable material so as to be elastically deformable by pressing said sheet-shaped material during the cutting operation; and second holding members disposed on opposite sides of said second blade, each of said second holding members being formed of self-deformable material so as to be elastically deformable to hold said sheet-shaped material during the cutting operation, said first holding members and said second holding members holding said sheet-shaped material from opposite surfaces thereof when cutting said sheet-shaped material by means of said first and second blades. It is therefore possible to prevent cracks from occurring on portions other than the cutting surface, and burrs from occurring on the cutting surface.
In accordance with the second aspect of the present invention, there may be adopted a structure in which each of said first blade and said second blade has a primary face and a secondary face, the primary face of said first blade being substantially aligned with the primary face of said second blade, and the secondary faces of said first blade and said second blade being directed to opposite directions to each other. With such a structure it is possible to prevent an excessively large stress from occurring on the sheet-shaped material even when the first and second blades come into contact with a cured portion of superfluous resin. As a result, the occurrence of cracks on the finished product side can be prevented.
In accordance with the third aspect of the present invention, there may be adopted a structure in which blade edges of the first and second blades do not come into contact with each other to form a gap between said blade edges when the first and second blades are in a closest proximity to each other. According to such a structure, it is possible to form notches on the opposite surfaces of the sheet-shaped material by means of the first and second blades during the first half of the single cutting process and then to break the portion of the sheet-shaped material, which corresponds to the above-mentioned gap between the blade edges, during the second half thereof. It is therefore possible to easily cut the sheet-shaped material including the substrate sheet formed of hard material.
In accordance with the fourth aspect of the present invention, there may be adopted a structure in which said second holding members comprise a front-side holding member, which is to be brought into contact with a finished product side of the sheet-shaped material and a rear-side holding member, which is to be brought into contact with a useless end portion side of the sheet-shaped material, said rear-side holding member having a smaller thickness than said front-side holding member in a non-deformed state. Such a structure provides a smooth shearing action by means of the first and second blades. The entire holding force by which the sheet-shaped material 5 is held d uring the cutting operation, is reduced, thus making it possible to prevent the sheet-shaped material from whitening.
In accordance with the fifth aspect of the present invention, there may be adopted a structure in which said first holding members comprise a front-side holding member, which is brought into contact with a finished product side of the sheet-shaped material and a rear-side holding member, which is brought into contact with a useless end portion side of the sheet-shaped material, and said rear side holding member has a laminate structure having a lower layer and an upper layer, said lower layer being formed of a higher hardness than said upper layer. Such a structure provides a smooth shearing action by means of the first and second blades.
In accordance with the sixth aspect of the present invention, the apparatus may further comprise displacement prevention members to prevent the holding members, which come into contact with the sheet-shaped material when cutting the sheet-shaped material by means of the first and second blades, from being displaced in a traveling direction of the sheet-shaped material. With these additional features, it is possible to prevent cracks from occurring on the finished product side.
In accordance with the sixth aspect of the present invention, the apparatus may further comprise a supply unit for supplying alternately the sheet-shaped materials from a plurality of supply sources to the first and second blades. With this additional feature, it is possible to reduce the period of time required to supply the sheet-shaped materials to the first and second blades in comparison with the case where the single sheet-shaped material is supplied from the single supply source to the cutting unit, thus improving the cutting efficiency.